Pressure relief valves are used in numerous applications where an over pressure event can have catastrophic effects. Such over pressure situations can lead to a rupture of the piping or pressure vessel and in certain situations explosion and fire. Pressure relief valves provide a safe way to release the contained fluid when the set pressure is exceeded.
Pressure relief valves come in many different forms. The most common are a simple valve that is held closed by a spring in compression. When the force on the valve exceeds the strength of the spring the valve opens to release the pressure. Once the pressure drops the spring returns the valve to a closed state. Thus the valve can be reused. This design is difficult to incorporate on larger diameter pressure relief valves that require an immediate opening valve.
Other pressure release valves rely on a disk that ruptures when the force of the pressure exceeds the strength of the disk. While this may work better on larger diameter lines, it requires a significant amount of time and labor to replace the disc. Thus the valve is not easily reset.
Butterfly valves have been used as pressure relief valves. They provide an effective way to release over pressure on a large diameter lines. However, their design limitations have proven inadequate for low and high pressure applications. These valves also have a history of being unreliable and difficult to seal. It has also proven difficult to obtain sufficient force or torque to close these valves.
What is needed, therefore, is an improved valve design that can be used on large diameter, low and high pressure lines that provides a reliable opening pressure. Further it would be beneficial to have a valve that can be easily closed after being triggered. Additional improvements are needed to ensure a reliable seal on these valves.